My invention comprises an improvement in a rack and pinion steering gear system of the kind shown, for example, in my U.S. Pat. No. 4,516,471. That patent describes a rack and pinion steering gear having a rack that is connected to the steering linkage of an automotive vehicle and a driving pinion under the control of the vehicle operator. The pinion actuates the rack in the direction of its axis. It is mounted in a steering gear housing by means of spaced bearings, and it is keyed or otherwise connected mechanically to the valve sleeve of a rotary valve mechanism. An inner valve member of the prior art system described in the U.S. Pat. No 4,516,471 is received in a valve sleeve and the inner valve member and sleeve are ported to provide a controlled flow of fluid pressure from a power steering pump to fluid flow passages that are adapted to distribute working pressure to either side of a piston for a fluid motor. The working piston of the fluid motor is connected to the rack and provides a fluid pressure assist during steering maneuvers.
A driver controlled steering shaft in prior art steering systems of this kind is connected to the pinion through a torsion rod which deflects under steering wheel torque. The inner valve member is connected directly to the steering shaft. Thus when torque is applied to the steering wheel and shaft, the inner valve member is displaced angularly with respect to the valve sleeve, thereby providing appropriate pressure distribution to the opposed sides of the motor piston.
It is conventional practice to straddle mount the pinion in the steering gear housing. The outboard end of the pinion disclosed in U.S. Pat. No. 4,516,471 is a ball bearing and the inboard side of the pinion is a fixed bushing. Gear tooth loads in such designs are transmitted from the pinion to the rack, thereby establishing a radial force vector that tends to displace the pinion in a direction transverse to its axis of oscillation.